/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.tribes.group.interceptors;

import org.apache.catalina.tribes.ChannelException;
import org.apache.catalina.tribes.Member;
import org.apache.catalina.tribes.group.AbsoluteOrder;
import org.apache.catalina.tribes.group.ChannelInterceptorBase;

import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A dinky coordinator, just uses a sorted version of the member array.
 *
 * @author rnewson
 */
public class SimpleCoordinator extends ChannelInterceptorBase {

	private Member[] view;

	private AtomicBoolean membershipChanged = new AtomicBoolean();

	private void membershipChanged() {
		membershipChanged.set(true);
	}

	@Override
	public void memberAdded(final Member member) {
		super.memberAdded(member);
		membershipChanged();
		installViewWhenStable();
	}

	@Override
	public void memberDisappeared(final Member member) {
		super.memberDisappeared(member);
		membershipChanged();
		installViewWhenStable();
	}

	/**
	 * Override to receive view changes.
	 *
	 * @param view
	 */
	protected void viewChange(final Member[] view) {
	}

	@Override
	public void start(int svc) throws ChannelException {
		super.start(svc);
		installViewWhenStable();
	}

	private void installViewWhenStable() {
		int stableCount = 0;

		while (stableCount < 10) {
			if (membershipChanged.compareAndSet(true, false)) {
				stableCount = 0;
			} else {
				stableCount++;
			}
			try {
				TimeUnit.MILLISECONDS.sleep(250);
			} catch (final InterruptedException e) {
				Thread.currentThread().interrupt();
			}
		}

		final Member[] members = getMembers();
		final Member[] view = new Member[members.length + 1];
		System.arraycopy(members, 0, view, 0, members.length);
		view[members.length] = getLocalMember(false);
		Arrays.sort(view, AbsoluteOrder.comp);
		if (Arrays.equals(view, this.view)) {
			return;
		}
		this.view = view;
		viewChange(view);
	}

	@Override
	public void stop(int svc) throws ChannelException {
		super.stop(svc);
	}

	public Member[] getView() {
		return view;
	}

	public Member getCoordinator() {
		return view == null ? null : view[0];
	}

	public boolean isCoordinator() {
		return view == null ? false : getLocalMember(false).equals(
				getCoordinator());
	}

}
